U.S. Pat. No. 6,930,818 discloses an electrophoretic display based on the microcup technology. The patent describes the manufacture of microcups as display cells, by microembossing or imagewise exposure. The microcups are then filled with an electrophoretic fluid comprising charged pigment particles dispersed in a solvent or solvent mixture.
The top openings of the microcups traditionally may have the same size and shape and such microcups spread across the entire display surface. For example, all of the microcups may have a top opening of a square shape on the viewing side or all of the microcups may have a top opening of a hexagonal shape on the viewing side. For this type of design, one disadvantage is that if the partition wall between the two neighboring microcups has a defect, the two microcups will become connected. As a result, the defective wall provides a fluid path for the particles to move from one microcup to the next microcup. Due to the pumping action of operating the display, one microcup will turn white and one black, producing a visual display defect.